1. Technical Field
This invention relates in general to telecommunications and, more particularly, to a method and apparatus for providing an expandable redundant database.
2. Description of the Related Art
Wireless telecommunications has been rapidly growing over the last several years. One of the most popular forms of wireless telecommunications is cellular telephony; however, other technologies, such as PHS (Personal Handyphone System) which is popular in Japan and is expected to have a significant impact in other parts of the world in the coming years.
PHS differs from cellular technology in that the mobile devices, such a telephones and modems, communicate through "base stations" which currently have a cell range (radius) of about 100-500 meters as opposed to a cell range of about 1500-5000 meters for a cellular cell. Accordingly, the distribution of base stations is much more dense than for cellular cells. However, the output of the PHS handsets can be significantly lower than cellular counterparts--a PHS handset has an output of about 10 milliwatts, while a cellular phone typically has an output of 0.6-1.0 watts. PHS is expected to offer superior features at a lower price in the near future.
In PHS systems, and other wireless telecommunications systems, one or more subscriber databases store information about each subscriber's account, such as service options (e.g. voice mail), restrictions (e.g. call blocking, long distance restrictions), billing information and status and current location (i.e., which base station is currently in contact with the subscriber's phone). The information in this database is necessary for all phone transactions, so the database is typically kept in fully redundant computers, such that a failure in one computer will not prevent access to the data. In order to guard against catastrophic failures, such as failures caused by flooding, earthquakes or other natural disasters, the redundant computers are often physically separated, often by hundreds of miles.
As the number of subscribers increase, the database size increases accordingly. Eventually, the database will be too large for a single computer to efficiently maintain.
Therefore, a need has arisen for a method and apparatus for providing an expandable subscriber database.